Elastic fluid turbine



March 17 1942: s. 5. (:00K ETAL 37 5 ELASTIC FLUID TURBINE Filed March4, 1940 Patented Mar. 17, 1942 ELASTIC FLUID TURBINE Stanley Smith Cookand Louis Mortimer Douglas, Wallsend-on-Tyne, England, assignors to TheParsons Marine Steam Turbine Company, Limited, Wallsend-on-Tyne, EnglandApplication March 4, 1940, Serial No. 322,194 In Great Britain March 4,1939 3 Claims.

This invention relates to elastic fluid turbines of the double flow typein which the direction of flow is in opposite directions in the twosections. 7

With such turbines of conventional construction, the duplicate flows areusually similar in every respect and symmetrically disposed about atransverse plane at mid length.

With such construction and with the rotor restrained axially by thethrust or adjusting block at one end in the usual manner, when thermalchanges occur in the operation, resulting in differential expansionbetween turbine and rotor, the clearances between the tips of -the rotorblades and the cylinder bore are increased in one half but arediminished in the other. As a consequence additional clearance must beprovided in order to enable the turbine to operate with safety.

The main object of the present invention is to provide constructions inwhich the clearance may be reduced without impairing safety.

The invention in brief consists in a double flow elastic fluid turbineof the type described in one flow portion of which the rotor blade tipslie in a conoidal surface, in the other flow portion the stator bladetips lie in a conoidal surface and the apices of both said conoidalsurfaces lie at the same end of the turbine.

The accompanying diagrammatic drawing illustrates in verticallongitudinal section a convenient construction of turbine embodying thepresent invention in one form.

In carrying the invention into effect according to the form illustratedin the accompanying drawing as applied to a central flow turbine inwhich the capacities of the two branches are equal we provide the rotorshaft a at one end with a collar 17 located axially by adjustable thrustfaces cd.

As regards the half of the rotor adjacent to the said collar, the rotoris formed as a cylindrical body e from which project radially the rowsof blades 1 and the tips of these blades lie in a somewhat conicalsurface or surfaces the larger diameter of which is at the end of therotor adjacent to the collar and the smaller diameter of which is at themiddle of the length of the rotor.

The associated half 9 of the encircling stator is correspondingly conedor tapered.

As regards the other half of the rotor, the rotor is formed as aconoidal body h from which project radially the rows of blades 2' andthe tips of these blades lie in a cylindrical surface or surfacesconcentric with the cylindrical internal face of the stator whilst thetips of the stator blades is lie on a conoidal surface or surfacesclosely adjacent to the external surface of the conoidal body h.

The two conoidal surfaces are co-extensive in the arrangement shown.

With this arrangement the varying clearances, i. e., those clearanceswhich vary with relative'axial movement of rotor and stator, on the halfe adjacent to the collar 1) are those between the tips of the movingblades f and the coned cylinder bore 9, and on the other half h arethose between the tips of the fixed blades is and the surfaces 7' of theconed rotor. In this case relative axial movement of rotor and statorcauses all the said clearances to be affected in the same way, that is,they are all diminished or all increased, with the result that they maybe set to have a minimum value when the greatest axial displacement hastaken place and may be arranged so that under any other conditions theseclearances increase. For instance, if the rotor expands more than thestator when heated up to full power service conditions, then the thrustblock faces ad will be so adjusted that the radial blade clearances area minimum under those full power service conditions.

At any other conditions where the thermal expansion is less the rotorwill retract from the stator towards the collar and these bladeclearances will all increase.

Should it be that the rotor expands less than the stator, then it wouldbe necessary to put the thrust block at the opposite end, that is to sayto dispose the conoidal surfaces so that their apices lie at the sameend of the turbine as the device for axially controlling the rotor.relatively to the stator.

In this case again the thrust block may be set so that the radial bladeclearances are at their minimum values under full power serviceconditions, i. e., when the temperature is at a maximum; under any lowertemperature conditions these clearances wouldlincrease.

In the example described above with reference to the accompanyingdrawing, the diameter of the annulus m between the rotor and stator ofone half of the turbine is substantially equal near the inlet region tothe annulus n of the other half, but if desired these annuli may insteadbe made substantially equal at the outlet ends.

Again, the two conoidal surfaces 9, 7' instead of being co-extensive maybe of different diameters at both ends.

The capacities of the two flow passages may be different if desired andin cases where they are so arranged that the axial thrusts on the rotordo not balance, dummies or other balancing devices may be employed inorder to relieve the axial force on the thrust block.

In all cases it is advisable to have a little residual thrust in onedirection in order definitely to locate the axial position of the rotorrelatively to the stator. Preferably the residual thrust is such as totend to reduce the clearances, The residual thrust is preferablyobtained by making the appropriate section greater in capacity or indiameter or in both capacity and diameter than the other section.

We claim:

1. A double flow elastic fluid turbine embodying a casing, twoopposed-flow stator sections in said casing, inward projectionsconstituting stator blades on each section, a rotor body lying in bothsections, outward projections on the rotor constituting rotor blades ineach section, the surface containing the tips of the rotor blades of onesection being conoidal and the surface containing the stator blades ofthat section being. cylindrical, the surface containing the rotor bladesin the other section being cylindrical and the surface containing thestator blades of that section conoidal and the apices of the two saidconoidal surfaces lying at the same end of the turbine.

2. A double flow elastic fluid turbine embodying a casing, twoopposed-flow stator sections in said casing, inward projectionsconstituting stator blades on each section, a rotor body lying in bothsections within the tips of the said projections, outward projections onthe rotor constituting rotor blades in each section, the surfacescontaining the tips of the blades being in one section conoidal in thecase of the rotor blades and cylindrical in the case of the statorblades and in the other section cylindrical in the case of the rotorblades and conoidal in the case of the stator blades and the apices ofthe two said conoidal surfaces lying at the same end of the turbine.

3. A double flow elastic fluid turbine embodying a casing, twoopposed-flow stator sections in said casing, inward projectionsconstituting stator blades on each section, a rotor body lying in bothsections, outward projections on the rotor constituting rotor blades ineach section, the surface containing the tips of the rotor blades of onesection being conoidal and the surface containing the stator blades ofthat section being cylindrical, the surface containing the rotor bladesin the other section being cylindrical and the surface containing thestator blades of that section conoidal, a thrust or axial-adjustmentdevice for one end of said rotor body, the apices of both conoidalsurfaces lying at the end of the turbine remote from that at which thesaid thrust or axial-adjustment device is disposed.

STANLEY SMITH COOK. LOUIS MORTIMER DOUGLAS.

